<!DOCTYPE html>
<!--  https://blog.csdn.net/qq_39327418/article/details/83654839  -->
<html lang="en">
<head>
    <style>
        .container {
            width: 310px;
            margin: 100px auto;
        }
        input {
            display: block;
            width: 290px;
            line-height: 40px;
            margin: 10px 0;
            padding: 0 10px;
            outline: none;
            border:1px solid #c8cccf;
            border-radius: 4px;
            color:#6a6f77;
        }
        #msg {
            width: 100%;
            line-height: 40px;
            font-size: 14px;
            text-align: center;
        }
        a:link,a:visited,a:hover,a:active {
            margin-left: 100px;
            color: #0366D6;
        }
        .block {
            position: absolute;
            left: 0;
            top: 0;
        }

        .sliderContainer {
            position: relative;
            text-align: center;
            width: 310px;
            height: 40px;
            line-height: 40px;
            margin-top: 15px;
            background: #f7f9fa;
            color: #45494c;
            border: 1px solid #e4e7eb;
        }

        .sliderContainer_active .slider {
            height: 38px;
            top: -1px;
            border: 1px solid #1991FA;
        }

        .sliderContainer_active .sliderMask {
            height: 38px;
            border-width: 1px;
        }

        .sliderContainer_success .slider {
            height: 38px;
            top: -1px;
            border: 1px solid #52CCBA;
            background-color: #52CCBA !important;
        }

        .sliderContainer_success .sliderMask {
            height: 38px;
            border: 1px solid #52CCBA;
            background-color: #D2F4EF;
        }

        .sliderContainer_success .sliderIcon {
            background-position: 0 0 !important;
        }

        .sliderContainer_fail .slider {
            height: 38px;
            top: -1px;
            border: 1px solid #f57a7a;
            background-color: #f57a7a !important;
        }

        .sliderContainer_fail .sliderMask {
            height: 38px;
            border: 1px solid #f57a7a;
            background-color: #fce1e1;
        }

        .sliderContainer_fail .sliderIcon {
            background-position: 0 -83px !important;
        }
        .sliderContainer_active .sliderText, .sliderContainer_success .sliderText, .sliderContainer_fail .sliderText {
            display: none;
        }

        .sliderMask {
            position: absolute;
            left: 0;
            top: 0;
            height: 40px;
            border: 0 solid #1991FA;
            background: #D1E9FE;
        }

        .slider {
            position: absolute;
            top: 0;
            left: 0;
            width: 40px;
            height: 40px;
            background: #fff;
            box-shadow: 0 0 3px rgba(0, 0, 0, 0.3);
            cursor: pointer;
            transition: background .2s linear;
        }

        .slider:hover {
            background: #1991FA;
        }

        .slider:hover .sliderIcon {
            background-position: 0 -13px;
        }

        .sliderIcon {
            position: absolute;
            top: 15px;
            left: 13px;
            width: 14px;
            height: 10px;
            background: url(../img/icon_light.f13cff3.png) 0 -26px;
            background-size: 34px 471px;
        }

        .refreshIcon {
            position: absolute;
            right: 0;
            top: 0;
            width: 34px;
            height: 34px;
            cursor: pointer;
            background: url(../img/icon_light.f13cff3.png) 0 -437px;
            background-size: 34px 471px;
        }

    </style>
    <meta charset="UTF-8">
    <title>Title</title>

</head>
<body>
<div class="container">
    <input value="admin" readonly/>
    <input type="password" value="1234567890" readonly/>
    <div id="captcha" style="position: relative"></div>
    <div id="msg"></div>
</div>
<script>
    (function (window) {
        const l = 42, // 滑块边长
            r = 10, // 滑块半径
            w = 310, // canvas宽度
            h = 155, // canvas高度
            PI = Math.PI
        const L = l + r * 2 // 滑块实际边长

        function getRandomNumberByRange(start, end) {
            return Math.round(Math.random() * (end - start) + start)
        }

        function createCanvas(width, height) {
            const canvas = createElement('canvas')
            canvas.width = width
            canvas.height = height
            return canvas
        }

        function createImg(onload) {
            const img = createElement('img')
            img.crossOrigin = "Anonymous"
            img.onload = onload
            img.onerror = () => {
                img.src = getRandomImg()
            }
            img.src = getRandomImg()
            return img
        }

        function createElement(tagName) {
            return document.createElement(tagName)
        }

        function addClass(tag, className) {
            tag.classList.add(className)
        }

        function removeClass(tag, className) {
            tag.classList.remove(className)
        }

        function getRandomImg() {
            return 'https://picsum.photos/300/150/?image=' + getRandomNumberByRange(0, 100)
        }

        function draw(ctx, operation, x, y) {
            ctx.beginPath()
            ctx.moveTo(x, y)
            ctx.lineTo(x + l / 2, y)
            ctx.arc(x + l / 2, y - r + 2, r, 0, 2 * PI)
            ctx.lineTo(x + l / 2, y)
            ctx.lineTo(x + l, y)
            ctx.lineTo(x + l, y + l / 2)
            ctx.arc(x + l + r - 2, y + l / 2, r, 0, 2 * PI)
            ctx.lineTo(x + l, y + l / 2)
            ctx.lineTo(x + l, y + l)
            ctx.lineTo(x, y + l)
            ctx.lineTo(x, y)
            ctx.fillStyle = '#fff'
            ctx[operation]()
            ctx.beginPath()
            ctx.arc(x, y + l / 2, r, 1.5 * PI, 0.5 * PI)
            ctx.globalCompositeOperation = "xor"
            ctx.fill()
        }

        function sum(x, y) {
            return x + y
        }

        function square(x) {
            return x * x
        }

        class jigsaw {
            constructor(el, success, fail) {
                this.el = el
                this.success = success
                this.fail = fail
            }

            init() {
                this.initDOM()
                this.initImg()
                this.draw()
                this.bindEvents()
            }

            initDOM() {
                const canvas = createCanvas(w, h) // 画布
                const block = canvas.cloneNode(true) // 滑块
                const sliderContainer = createElement('div')
                const refreshIcon = createElement('div')
                const sliderMask = createElement('div')
                const slider = createElement('div')
                const sliderIcon = createElement('span')
                const text = createElement('span')

                block.className = 'block'
                sliderContainer.className = 'sliderContainer'
                refreshIcon.className = 'refreshIcon'
                sliderMask.className = 'sliderMask'
                slider.className = 'slider'
                sliderIcon.className = 'sliderIcon'
                text.innerHTML = '向右滑动滑块填充拼图'
                text.className = 'sliderText'

                const el = this.el
                el.appendChild(canvas)
                el.appendChild(refreshIcon)
                el.appendChild(block)
                slider.appendChild(sliderIcon)
                sliderMask.appendChild(slider)
                sliderContainer.appendChild(sliderMask)
                sliderContainer.appendChild(text)
                el.appendChild(sliderContainer)

                Object.assign(this, {
                    canvas,
                    block,
                    sliderContainer,
                    refreshIcon,
                    slider,
                    sliderMask,
                    sliderIcon,
                    text,
                    canvasCtx: canvas.getContext('2d'),
                    blockCtx: block.getContext('2d')
                })
            }

            initImg() {
                const img = createImg(() => {
                    this.canvasCtx.drawImage(img, 0, 0, w, h)
                    this.blockCtx.drawImage(img, 0, 0, w, h)
                    const y = this.y - r * 2 + 2
                    const ImageData = this.blockCtx.getImageData(this.x, y, L, L)
                    this.block.width = L
                    this.blockCtx.putImageData(ImageData, 0, y)
                })
                this.img = img
            }

            draw() {
                // 随机创建滑块的位置
                this.x = getRandomNumberByRange(L + 10, w - (L + 10))
                this.y = getRandomNumberByRange(10 + r * 2, h - (L + 10))
                draw(this.canvasCtx, 'fill', this.x, this.y)
                draw(this.blockCtx, 'clip', this.x, this.y)
            }

            clean() {
                this.canvasCtx.clearRect(0, 0, w, h)
                this.blockCtx.clearRect(0, 0, w, h)
                this.block.width = w
            }

            bindEvents() {
                this.el.onselectstart = () => false
                this.refreshIcon.onclick = () => {
                    this.reset()
                }

                let originX, originY, trail = [], isMouseDown = false
                this.slider.addEventListener('mousedown', function (e) {
                    originX = e.x, originY = e.y
                    isMouseDown = true
                })
                document.addEventListener('mousemove', (e) => {
                    if (!isMouseDown) return false
                const moveX = e.x - originX
                const moveY = e.y - originY
                if (moveX < 0 || moveX + 38 >= w) return false
                this.slider.style.left = moveX + 'px'
                var blockLeft = (w - 40 - 20) / (w - 40) * moveX
                this.block.style.left = blockLeft + 'px'

                addClass(this.sliderContainer, 'sliderContainer_active')
                this.sliderMask.style.width = moveX + 'px'
                trail.push(moveY)
            })
                document.addEventListener('mouseup', (e) => {
                    if (!isMouseDown) return false
                isMouseDown = false
                if (e.x == originX) return false
                removeClass(this.sliderContainer, 'sliderContainer_active')
                this.trail = trail
                const {spliced, TuringTest} = this.verify()
                if (spliced) {
                    if (TuringTest) {
                        addClass(this.sliderContainer, 'sliderContainer_success')
                        this.success && this.success()
                    } else {
                        addClass(this.sliderContainer, 'sliderContainer_fail')
                        this.text.innerHTML = '再试一次'
                        this.reset()
                    }
                } else {
                    addClass(this.sliderContainer, 'sliderContainer_fail')
                    this.fail && this.fail()
                    setTimeout(() => {
                        this.reset()
                    }, 1000)
                }
            })
            }

            verify() {
                const arr = this.trail // 拖动时y轴的移动距离
                const average = arr.reduce(sum) / arr.length // 平均值
                const deviations = arr.map(x => x - average) // 偏差数组
                const stddev = Math.sqrt(deviations.map(square).reduce(sum) / arr.length) // 标准差
                const left = parseInt(this.block.style.left)
                return {
                    spliced: Math.abs(left - this.x) < 10,
                    TuringTest: average !== stddev, // 只是简单的验证拖动轨迹，相等时一般为0，表示可能非人为操作
                }
            }

            reset() {
                this.sliderContainer.className = 'sliderContainer'
                this.slider.style.left = 0
                this.block.style.left = 0
                this.sliderMask.style.width = 0
                this.clean()
                this.img.src = getRandomImg()
                this.draw()
            }

        }

        window.jigsaw = {
            init: function (element, success, fail) {
                new jigsaw(element, success, fail).init()
            }
        }
    }(window))

    jigsaw.init(document.getElementById('captcha'), function () {
        document.getElementById('msg').innerHTML = '登录成功！'
    })

</script>
</body>
</html>